Using Pantheon and Hubble parameter data to constrain the Ricci dark energy in a Bianchi I Universe

In this work, we use the most recent publicly available type Ia supernova (SNIa) compilations and H(z) data. A well formulated cosmological model based on Bianchi type I (BI) metric is implemented in the presence of the Ricci dark energy model. Using the maximum likelihood technique, we estimate the present value of Hubble's constant H₀ = 70.339 ± 0.743, matter density parameter ${{\rm{\Omega }}}_{{m}_{0}}=0.297\pm 0.031$, anisotropy parameter ${{\rm{\Omega }}}_{{\sigma }_{0}}=\,$−0.004 01 ± 0.001 07 within $1\sigma ^{\prime} $ confidence level by bounding our derived model with recent joint Pantheon and H(z) data. We have constrained the present value of the equation of state parameter as ω_de = −1.17 joint with the observational data. The present value of the deceleration parameter of the Universe in the derived model is obtained as ${q}_{0}=-{0.749}_{-0.086}^{+0.076}$. Transition redshift is also derived as ${z}_{\mathrm{tr}}\sim 0.551$ with the recent observations (Pantheon + H(z)) datasets. Finally, we compare the anisotropy effects on the evolution of H(z) for the proposed model under consideration with different observational datasets.     

Neutrino astronomy and massive long-lived particles from the big bang

We consider the neutrino flux from the decay of long-lived big-bang particles. The red-shift z_tr at which the neutrino transparency of the universe sets in is calculated as a function of neutrino energy: z_tr 1 × 10⁵ for TeV neutrinos and z_tr 3 × 10⁶ for 10 MeV neutrinos. One might expect the production of detectable neutrino flux at z z_tr, but, as demonstrated in this paper, the various upper limits, most notably due to nucleosynthesis and diffuse X- and gamma-rays, preclude this possibility. Unless the particle decay is strongly dominated by the pure neutrino channel, observable neutrino flux can be produced only at the current epoch, corresponding to red-shift z ≈ 0. For the thermal relics which annihilate through the gauge bosons of SU(3)×SU(2)×U(1) group, the neutrino flux can be marginally detectable at 0.1 < E_v < 10 TeV. As an example of non-thermal relics we consider gravitinos. If gravitinos are the lightest supersymmetric particles (LSP) they can produce the detectable neutrino flux in the form of a neutrino line with energy , where M_G is the gravitino mass. The flux strongly depends on the mechanisms of R-parity violation. It is shown that heavy gravitinos (M_G 100 GeV) can make up the dark matter in the universe.     

Anisotropy Effects and Observational Data on the Constraints of Evolution Dark Energy Models

We investigate cosmological dark energy models where the accelerated expansion of the universe is driven by a field with an anisotropic universe. The constraints on the parameters are obtained by maximum likelihood analysis using observational of 194 Type Ia supernovae(SNIa) and the most recent joint light-curve analysis(JLA) sample. In particular we reconstruct the dark energy equation of state parameter w(z) and the deceleration parameter q(z). We find that the best fit dynamical w(z) obtained from the 194 SNIa dataset does not cross the phantom divide line w(z) =-1 and remains above and close to w(z)≈-0.92 line for the whole redshift range 0 ≤ z ≤ 1.75 showing no evidence for phantom behavior. By applying the anisotropy effect on the ΛCDM model, the joint analysis indicates that ?_(σ0)= 0.0163 ± 0.03,with 194 SNIa, ?_(σ0)=-0.0032 ± 0.032 with 238 the SiFTO sample of JLA and ?_(σ0)= 0.011 ± 0.0117 with 1048 the SALT2 sample of Pantheon at 1σ′confidence interval. The analysis shows that by considering the anisotropy, it leads to more best fit parameters in all models with JLA SNe datasets. Furthermore, we use two statistical tests such as the usual χ_(min)~2/dof and p-test to compare two dark energy models with ΛCDM model. Finally we show that the presence of anisotropy is confirmed in mentioned models via SNIa dataset.     

Some properties of the spectral flow in semiriemannian geometry

Let be the action integral on a semiriemannian manifold ( , g) defined on the space of the curves z : [0, 1] → joining two given points z₀ and z₁. The critical points of ƒ are the geodesics joining z₀ and z₁. Let s ε [0, 1]. We study the behavior, in dependence of s, of the eigenvalues of the Hessian form of ƒ evaluated at z, restricted to the interval [0, s]. A formula for the derivative of the eigenvalues is given and some applications are shown.     

Magnetic behaviour of some Mn.III2.VI4 compounds and their alloys

Measurement of the magnetic susceptibility χ as a function of temperature were made on polycrystalline samples from the alloy systems Cd_1−zMn_zGa₂Se₄, Zn_1−zMn_zGa₂Se₄ and Cd_1−zMn_zIn₂Te₄ which had been subjected to various heat treatments. The 1/χ versus T curves indicated that for the Zn---Se alloys, for all values of z, samples slowly cooled to room temperature were antiferromagnetic showing ideal Curie-Weiss behaviour, but for samples quenched from 700°C the behaviour was a mixture of antiferromagnetic and spin-glass. For the Cd---Se alloys, samples from the range (0.6 < z < 1.0) showed very similar behaviour, but in the range (0 < z < 0.6) even the very slowly cooled samples showed a mixture of antiferromagnetic and spin-glass behaviour. For the Cd---Te alloys, all samples, however heat-treated, showed spin-glass form. Values of the Curie-Weiss constant Ф were determined from all of the 1/χ versus T curves, and by comparison with the T(z) phase diagrams for the different alloy systems, the values of Ф were correlated with the ordering of the Mn atoms on the cation lattice. It is shown that the experimental values of Ф can give a very convenient way of determining the type of ordering and the degree of order in such alloys.     

Effect of cobalt substitution on cationic distribution in LiNi1 − y CoyO2 electrode materials

A crystal chemistry study of LiNi_{1 − y}Co_yO₂ phases, used as positive electrode in lithium batteries, is presented. These materials crystallize in the rhombohedral system (space group: R m) with a layered structure. Rietveld profile refinement of the X-ray data shows that for low substitution amounts ( ≤ 0.20) extra-nickel ions are always present leading to the Li_{1 − z}Ni_{1 + z − t}CotO₂ (t = y(1 + z)) formula (z * > 0), while for y ≥ 0.30, a pure 2D structure is obtained (z = 0). The stabilization of the 2D character of the structure by cobalt substitution in lithium nickelate leads to the improvement of the electrochemical properties.     

Constraints on neutrino mass in the scenario of vacuum energy interacting with cold dark matter after Planck 2018

In this work, we investigate the constraints on the total neutrino mass in the scenario of vacuum energy interacting with cold dark matter (abbreviated as IΛCDM) by using the latest cosmological observations. We consider four typical interaction forms, i.e. $Q=\beta H{\rho }_{\mathrm{de}}$, $Q=\beta H{\rho }_{{\rm{c}}}$, $Q=\beta {H}_{0}{\rho }_{\mathrm{de}}$, and $Q=\beta {H}_{0}{\rho }_{{\rm{c}}}$, in the IΛCDM scenario. To avoid the large-scale instability problem in interacting dark energy models, we employ the extended parameterized post-Friedmann method for interacting dark energy to calculate the perturbation evolution of dark energy in these models. The observational data used in this work include the cosmic microwave background (CMB) measurements from the Planck 2018 data release, the baryon acoustic oscillation (BAO) data, the type Ia supernovae (SN) observation (Pantheon compilation), and the 2019 local distance ladder measurement of the Hubble constant H₀ from the Hubble Space Telescope. We find that, compared with those in the ΛCDM+$\sum {m}_{\nu }$ model, the constrains on $\sum {m}_{\nu }$ are looser in the four IΛCDM+$\sum {m}_{\nu }$ models. When considering the three mass hierarchies of neutrinos, the constraints on $\sum {m}_{\nu }$ are tightest in the degenerate hierarchy case and loosest in the inverted hierarchy case. In addition, in the four IΛCDM+$\sum {m}_{\nu }$ models, the values of coupling parameter β are larger using the CMB+BAO+SN+H₀ data combination than that using the CMB+BAO+SN data combination, and β>0 is favored at more than 1σ level when using CMB+BAO+SN+H₀ data combination. The issue of the H₀ tension is also discussed in this paper. We find that, compared with the ΛCDM+$\sum {m}_{\nu }$ model, the H₀ tension can be alleviated in the IΛCDM+$\sum {m}_{\nu }$ model to some extent.     

Effects of crystallographic ordering on the magnetic behaviour of (AgIn)1-zMn2zTe2 and (CuIn)1-zMn2zTe2 alloys

Measurements of magnetic susceptibility in the temperature range 4.2–300 K were made on polycrystalline samples of the (AgIn)_{1 - z}Mn_2zTe₂ and (CuIn)_{1 - z}Mn_2zTe₂ alloys, and the data used to give values of spin-glass transition te mperature T_g and Curie-Weiss paramagnetic temperature θ. For any sample for which the X-ray powder photograph indicated an apparently single phase condition, either zinc-blende or chalcopyrite, the susceptibility data could show up to three separate T_g values. These different magnetic conditions are attributed to crystallographic ordering of the Mn ions on the chalcopyrite and zinc-blende lattices, the three observed T_g values corresponding to disordered zinc-blende, ordered zinc-blende and ordered chalcopyrite. The value of θ obtained from the 1/χ vs. T plot is shown to be a weighted mean of the separate values of θ for the phases present. The relative sizes of the T_g peaks and the values of θ for any given sample gives an indication of the amount of each phase present. These amounts were varied by using different methods of heat treatment and it was shown that the magnetic behaviour was consistent with the T(z) phase diagram for the two alloy systems.     

Vortex phases and dynamics in high-temperature and conventional amorphous superconductors

The vortex phases and dynamics of high-temperature and conventional amorphous superconductors are investigated over a broad frequency range. A second-order vortex-solid melting transition in both YBa₂Cu₃O₇ single crystals with random point defects and amorphous Mo₃Si films is manifested by a set of universal critical exponents (ν≈2/3 and z≈3) from both ac and dc transport as well as ac magnetic susceptibility measurements. In contrast, the melting transition in YBa₂Cu₃O₇ single crystals with correlated columnar defects is found to be consistent with a Bose-glass phase transition characterized by a different set of critical exponents (ν≈1/2 and z′≈4).     

外加电场和Al组分对纤锌矿AlGaN/GaN量子阱中的电子g因子的影响

研究了外加电场和垒层的Al组分对AlGaN/GaN量子阱中的横向和纵向g因子(g⊥和g//)及其各向异性(δg)的影响.纤锌矿体结构的贡献(S_//~(bulk)和g⊥)是构成g⊥=(g//-g_0)=g_//~(bulk)的主要部分,但g_//~(bulk)和g⊥的差值很小且几乎不随外加电场和Al组分改变.当外加电场的方向同极化电场的方向相同(相反)且增加时,g_//~(bulk)和g_⊥~(bulk)的强度同时增加(减小).当外加电场从-1.5×10~8 V·m~(-1)到1.5×10~8 V·m~(-1)变化时,异质结界面对g⊥的贡献(Γ_(Inter))大于0且强度缓慢增加,阱层对g⊥的贡献(Γ_W)小于0且强度也缓慢增加.然而Γ_(Inter)的强度比Γ_w大,且后者的强度随着外加电场的改变增加较快,所以δg0且强度随着外加电场的变化而减小.当垒层的Al组分增加时,如果不考虑应变效应(S_(1,2)=0),g_//~(bulk)和g⊥的强度同时减小,然而考虑应变效应后(S_(1,2)≠0),β_1g⊥和γ1(g_//~(bulk))的强度随着Al组分的增加而增加.随着垒层Al组分的增加,Γ_(Inter)和Γ_w的强度都增加,但Γ_(Inter)的强度较大且增加得较快,所以的的强度缓慢增加.g⊥的强度先随着Al组分的增加而减小,然后又随着Al组分的增加而增加,因为g⊥小于0且强度随着Al组分增加得很快.结果表明,AlGaN/GaN量子阱结构中的电子g因子及其各向异性可以被外加电场、垒层的Al组分、应变效应和量子限制效应共同调制.     

Superconductivity in Ba2−xSrxYCu3Oz prepared at GPa

The compounds Ba_1.4Sr_0.6YCu₃O_z (7.0≤z<7.4) were synthesized at 2 GPa to clarify the effect of high temperature and pressure on the superconducting properties. The structure as observed by powder X-ray diffraction was tetragonal for z≥7.2, and orthorhombic or tetragonal for z<7.1. It has been revealed that high-pressure syntheses suppress the superconductivity in the compounds with z<7.1. Recovery of the superconducting properties occurs above z≥7.2. The effect of Sr substitution on the superconducting properties was also studied. The magnitude of diamagnetism at 5–30 K decreases monotonically from −0.003 to −0.0002 emu/g Oe with increasing x in Ba_2−xSr_xYCu₃O_z (x≥1.2).     

Influence of Nd substitution on the superconducting properties of ceramics in the 2212 system Bi2−wPbwSr2−xCa1−yNdx+yCu2O8+z

In the system Bi_2−wPb_wSr_2−xCa_1−yNd_x+yCu₂O_8+z different fractions of Nd are substituted on either Sr of Ca sites in order to introduce intrinsic insulating pinning centres. It is shown that a Nd concentration around x or y = 0.2 is likewise favourable with an average Nd---Nd distance in the range of the coherence length in the a, b-plane. However, clear evidence of flux pinning is only present for charge compensation with Pb²⁺. A simultaneous substitution of the Bi-based 2212 superconductor with moderate amounts of Nd³⁺ and Pb²⁺ improves the superconducting properties by strengthening the flux pinning forces.     

Surface structures of equilibrium restricted curvature model on two fractal substrates

With the aim to probe the effects of the microscopic details of fractal substrates on the scaling of discrete growth models, the surface structures of the equilibrium restricted curvature(ERC) model on Sierpinski arrowhead and crab substrates are analyzed by means of Monte Carlo simulations. These two fractal substrates have the same fractal dimension df, but possess different dynamic exponents of random walk zrw. The results show that the surface structure of the ERC model on fractal substrates are related to not only the fractal dimension df, but also to the microscopic structures of the substrates expressed by the dynamic exponent of random walk zrw. The ERC model growing on the two substrates follows the well-known Family–Vicsek scaling law and satisfies the scaling relations 2α + df≈ z ≈ 2zrw. In addition, the values of the scaling exponents are in good agreement with the analytical prediction of the fractional Mullins–Herring equation.     

The dispersion properties of surface acoustic wave devices on AlN/LiNbO3 film/substrate structure

Highly c-axis oriented aluminum nitride (AlN) films were deposited on z-cut LiNbO₃ substrates by reactive rf magnetron sputtering. The crystalline properties investigated by X-ray diffraction (XRD) revealed that AlN film with (0 0 2) preferred orientation was improved by an increase of the deposition time within the experimental range. However, the surface morphology of AlN film measured by scanning probe microscopy (SPM) showed that the roughness was getting worse with increase of deposition time. Surface acoustic wave (SAW) properties, measured by a network analyzer in the structure consisting of highly c-axis AlN films on z-cut LiNbO₃ substrates, were investigated. The phase velocity (V_P) was significantly increased by the increase of h/λ, where h is the thickness of AlN film and λ is the wavelength. However, the insertion loss (IL) of SAW filters was also increased by the increase of h/λ. Experimental results on the temperature characteristics of SAW devices are also presented.     

Consistency of optimizing finite-time Carnot engines with the low-dissipation model in the two-level atomic heat engine

The efficiency at the maximum power (EMP) for finite-time Carnot engines established with the low-dissipation model, relies significantly on the assumption of the inverse proportion scaling of the irreversible entropy generation ΔS^(ir) on the operation time τ, i.e. ΔS^(ir) ∝ 1/τ. The optimal operation time of the finite-time isothermal process for EMP has to be within the valid regime of the inverse proportion scaling. Yet, such consistency was not tested due to the unknown coefficient of the 1/τ-scaling. In this paper, we reveal that the optimization of the finite-time two-level atomic Carnot engines with the low-dissipation model is consistent only in the regime of η_C < 2(1 − δ)/(1 + δ), where η_C is the Carnot efficiency, and δ is the compression ratio in energy level difference of the heat engine cycle. In the large-η_C regime, the operation time for EMP obtained with the low-dissipation model is not within the valid regime of the 1/τ-scaling, and the exact EMP of the engine is found to surpass the well-known bound η₊ = η_C/(2 − η_C).     

Redshift drift constraints on f(T) gravity

We explore the impact of the Sandage−Loeb (SL) test on the precision of cosmological constraints for f(T) gravity theories. The SL test is an important supplement to current cosmological observations because it measures the redshift drift in the Lyman-α forest in the spectra of distant quasars, covering the “redshift desert” of 2≲z≲5. To avoid data inconsistency, we use the best-fit models based on current combined observational data as fiducial models to simulate 30 mock SL test data. We quantify the impact of these SL test data on parameter estimation for f(T) gravity theories. Two typical f(T) models are considered, the power-law model f(T)_PL and the exponential-form model f(T)_EXP. The results show that the SL test can effectively break the existing strong degeneracy between the present-day matter density Ω_m and the Hubble constant H₀ in other cosmological observations. For the considered f(T) models, a 30-year observation of the SL test can improve the constraint precision of Ω_m and H₀ enormously but cannot effectively improve the constraint precision of the model parameters.     

Oxygen nonstoichiometry and phase transitions of the neodymium-rich Nd1+xBa2−xCu3Oz solid solution

On the basis of chemical, thermal analysis and Cu K-edge X-ray absorption measurements, oxygen content in the Nd_1+xBa_2−xCu₃O_z solid solution was determined between 1000°C in air and 400°C in oxygen for x=0.05–0.9 compositions. It has been observed that the oxygen nonstoichiometry Δz of the Nd_1+xBa_2−xCu₃O_7+x/2−Δz solid solution decreases 2–2.5 times for a large substitution (Δz≈0.3–0.33 for x=0.9), despite of the acclaimed higher total oxygen content. The difference in nonstoichiometry is explained by a higher average value of the copper oxidation state (ACV), which is vital for the solid solution with large x even at elevated temperatures (ACV≈2–2.05 for x>0.3 at 1000°C, PO₂=0.21 atm). On the contrary, the ACV after complete oxygenation is almost constant (about 2.25–2.3) for the whole series. The x-dependence of the oxygen content is not monotonous and structural phase transitions can be observed at x=0.3 and x=0.6, as confirmed by the X-ray diffraction and the Raman scattering spectroscopy. The first well-known transition is connected with the oxygen disorder due to the Nd substitution for Ba at random Ba-sites. In the present work, it is proved by the apical oxygen mode broadening in Raman spectra. Ordering of the Nd and Ba atoms with a subsequent orthorhombic distortion of the lattice may occur even at 1000°C in air due to the second transformation at x≈0.6. The invariable orthorhombicity of the Nd-rich solid solution with x>0.6 is not caused by the oxygen absorption as in the x=0.05 case. Existence of high- and low-temperature orthorhombic modifications of this solid solution has been observed for the first time. Finally, a tentative 3D (z–x–T) diagram is suggested for the Nd_1+xBa_2−xCu₃O_z solid solution up to 1000°C in air, including the new x=0.6–0.9 region.     

BaTi2Bi2O的电子结构与磁性

采用第一性原理方法,对BaTi₂Bi₂O的电子结构和磁性进行计算.非磁性态的计算结果显示:费米能级处的态密度主要来自d_z²,d_x²-y²和d_xy三个轨道,同时费米面也主要有三部分组成,并且将其沿着矢量q₁=(π/a,0,0)和q₂=(0,π/a,0)平移时,第三部分费米面(沿着X-R连线)与第一部分费米面(M-A连线)嵌套明显,计算得出磁化系数χ₀(q)在X点出现峰值,与峰值出现在M点的FeAs基超导体不同.上述磁化率峰值可以诱导产生自旋密度波,使得BaTi₂Bi₂O材料的磁性基态是bi-collinear antiferromagnetism(AF3)与blocked checkerboard antiferromagnetism(AF4)的二度简并态.随着空穴掺杂,χ₀(q)的峰值降低,而电子掺杂则导致峰值变大.当自旋涨落被完全压制时,超导出现,这可以解释为什么超导只出现在空穴掺杂型化合物而非电子掺杂型.     

Study of K*(892)0 and φ (1020) meson production in proton-proton and Pb-Pb collisions at $\sqrt{{s}_{NN}}$=2.76 TeV

In this paper, we describe a study of charged particle yield as a function of p_T for K^*(892)⁰ and φ (1020) mesons in proton-proton (pp) and Pb-Pb collisions at $\sqrt{{s}_{NN}}$=2.76 TeV in the central rapidity region of ∣y∣<0.5, in a p_T range of 0<p_T <15 GeV c⁻¹ in pp collisions and in a p_T range of 0<p_T<20 GeV c⁻¹ in Pb-Pb collisions. We also investigated a very important ratio, the nuclear modification factor, to study the effects of the medium in the most central region, i.e. 0%-5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models’ simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for $\sqrt{{s}_{NN}}$=2.76 TeV. It was concluded that the models’ predictions for the φ-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with p_T. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K^*0 mesons, both programs gave almost the same predictions, and with p_T in the interval p_T>3 GeV c⁻¹, the predictions were very close to the experimental data. Both models gave higher predictions for the soft p_T interval and lower predictions for the hard interactions. The values of the R_AA distributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the p_T distributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K^*0 at low values of p_T with respect to φ-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for R_AA in the region from p_T =10 GeV c⁻¹ to 20 GeV c⁻¹ observed by the ALICE experiment was absent for the φ-mesons.     

Magnetic ordering in U4Cu4P7 single crystal

The magnetic ordering in the tetragonal ternary compound U₄Cu₄P₇ has been studied by neutron diffraction. It orders below T_N = 146 K with an antiferromagnetic structure of wave vector k = (001). The magnetic ordering corresponds to a stacking of ferromagnetic (001) uranium planes according to the sequences m₁, m₁, m₂, -m₂, -m₁, -m₁, -m₂, m₂ where m₁ and m₂ represent the magnetic moment, directed along the tetragonal axis of the two uranium sites U(1) (0,0,± z₁) and U(2) (0,0, ± z₂) respectively. The magnetic moments on these two sites have different temperature dependencies as well as well as they reach the different values of 1.1 and 2.2.μ_B for the U(1) and U(2) sites, respectively.